Electrophotographic photosensitive drum process cartridge and electrophotographic image forming apparatus

ABSTRACT

An electrophotographic photosensitive drum for a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, wherein the process cartridge includes a charging roller for electrically charging the photosensitive drum and a developing roller for developing a latent image formed on the drum, the drum includes a drum helical gear, mounted to one end of the cylinder, for transmiting a rotational driving force to a transfer roller provided in a main assembly for transmiting a rotational driving force to the charging roller and the developing roller, wherein a shaft portion provided at a central portion of the drum helical gear at a position where it is completely overlapped with a teeth of the drum helical gear with respect to a longitudinal direction of the cylinder, wherein a gap is provided between the teeth and a peripheral surface of the shaft portion; a projection, provided at a free end of the shaft portion, for engagement with a hole formed in the main assembly to receive a driving force from the main assembly when the process cartridge is mounted to the main assembly; the drum, when it is mounted to a cartridge frame of the cartridge, permits insertion of the cartridge frame to enter the gap so that shaft portion is rotatably supported in the cartridge frame.

FIELD OF THE INVENTION AND RELATED ART

[0001] The present invention relates to a process cartridge detachably mountable to an electrophotographic image forming apparatus, an electrophotographic image forming apparatus and an electrophotographic photosensitive drum for the electrophotographic image forming apparatus and the process cartridge.

[0002] The electrophotographic image forming apparatus forms an image on a recording material through an electrophotographic image formation type process.

[0003] Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (laser beam printer, LED printer or the like), the facsimile machine, a word processor or a complex machine (multi-function printer or the like) or the like.

[0004] The process cartridge is a cartridge which contains as a unit charging means, developing means and an electrophotographic photosensitive member and which is detachably mountable to a main assembly of an image forming apparatus.

[0005] Furthermore, the process cartridge may be a cited reference containing at least developing means, charging means and an electrophotographic photosensitive member as a unit which is detachably mountable to the image forming apparatus.

[0006] The process cartridge type is advantageous in that maintenance operations can be performed not by a service person but by the user in effect, and therefore, operation property has been significantly improved.

[0007] Therefore, the process cartridge type is widely used in the field of image forming apparatus.

[0008] In order to provide satisfactory images by the electrophotographic image forming apparatus using such a process cartridge, it is necessary that process cartridge is mounted at a predetermined position in the main assembly of the electrophotographic image forming apparatus to establish correct connection of the interface portions such as various electrical contacts and a drive transmitting portion.

[0009] Referring first to FIG. 31, there is shown a process cartridge CR, and FIG. 32 designates a cartridge guide GL provided in the main assembly PR of the image forming apparatus.

[0010]FIG. 33 shows an image forming apparatus employing of such a process cartridge PC.

[0011] As shown in FIG. 31-FIG. 33, for mounting and demounting of the process cartridge CR relative to the main assembly PR of the image forming apparatus, a positioning boss CB is provided across the axis of the photosensitive drum which is the electrophotographic photosensitive member, and the main assembly PR of the image forming apparatus is provided with a mounting guide GL for guiding and positioning the positioning boss CB. When the user inserted the process cartridge CR to a predetermined position along the cartridge mounting guide GL, an abutting portion P provided in the main assembly PR of the image forming apparatus is abutted by the process cartridge CR such that rotation of process cartridge CR about the positioning boss CB is prevented. The apparatus of such a structure has been put into practice.

[0012] The present invention provides a further development of such art.

SUMMARY OF THE INVENTION

[0013] Accordingly, it is a principal object of the present invention to provide a process cartridge, an electrophotographic image forming apparatus and a photosensitive drum for the process cartridge and the electrophotographic image forming apparatus, wherein a photosensitive drum, a charging roller, a developing roller and a transfer roller provided in t process cartridge can be stably driven. It is another object of the present invention to provide a process cartridge, an electrophotographic image forming apparatus and a photosensitive drum for the process cartridge and the electrophotographic image forming apparatus, wherein a strength of the drum gear can be improved.

[0014] It is a further object of the present invention to provide a process cartridge, electrophotographic image forming apparatus and a photosensitive drum for the process cartridge and the electrophotographic image forming apparatus, in which a charging roller can be rotated as well as the photosensitive drum, the developing roller and the transfer roller.

[0015] According to an aspect of the present invention, there is provided an electrophotographic photosensitive drum for a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, wherein said process cartridge includes a charging roller for electrically charging said photosensitive drum and a developing roller for developing an electrostatic latent image formed on said photosensitive drum, said photosensitive drum comprising (i) a cylinder having a photosensitive layer on the peripheral surface thereof; (ii) a drum helical gear, mounted to one end of said cylinder, for transmiting a rotational driving force to a transfer roller provided in a main assembly of said apparatus and for transmiting a rotational driving force to said charging roller and said developing roller, wherein the transfer roller is effective to transfer the developed image formed on said electrophotographic photosensitive drum onto a recording material; (iii) a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth or said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; (iv) a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; wherein said electrophotographic photosensitive drum, when it is mounted to a cartridge frame of said process cartridge, permits insertion of the cartridge frame to enter said gap so that shaft portion is rotatably supported in said cartridge frame.

[0016] These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic sectional view of the image forming apparatus in one of the preferred embodiments of the present invention, in which a process cartridge in accordance with the present invention has been properly mounted, describing the general structure thereof.

[0018]FIG. 2 is a schematic sectional view of the process cartridge in the preferred embodiment of the present invention, describing the structure. thereof.

[0019]FIG. 3 is a perspective view of the process cartridge in accordance with the present invention, in FIG. 2.

[0020]FIG. 4 is another perspective view of the process cartridge in accordance with the present invention, in FIG. 2.

[0021]FIG. 5 is an exploded perspective view of the drum frame unit of the process cartridge in accordance with the present invention.

[0022]FIG. 6 is a perspective view of the drum frame unit of the process cartridge in accordance with the present invention.

[0023]FIG. 7 is a perspective view of the side holder of the drum frame unit.

[0024]FIG. 8 is a plan view of the charge roller driving means, describing the structure thereof.

[0025]FIG. 9 is an exploded perspective view of the charge roller driving means, describing the structure thereof.

[0026]FIG. 10 is a perspective view of the process cartridge driving mechanism, in the preferred embodiment of the present invention.

[0027]FIG. 11 is a schematic sectional view of the gear train of the process cartridge driving mechanism in FIG. 10, describing the structure thereof.

[0028]FIG. 12 is a plan view or the gear train of the process cartridge driving mechanism in FIG. 10, describing the structure thereof.

[0029]FIG. 13 is a perspective view of the process cartridge driving mechanism, in another embodiment of the present invention, describing the structure thereof.

[0030]FIG. 14 is a schematic sectional view of the process cartridge driving mechanism in FIG. 13, describing the structure thereof.

[0031]FIG. 15 is a plan view of the process cartridge driving mechanism in FIG. 13, describing the structure thereof.

[0032]FIG. 16(a) is a perspective view of the toner sealing member in the preferred embodiment of the present invention, and FIG. 16(b) is a sectional view of the same toner sealing member.

[0033]FIG. 17 is a perspective view of the toner storage-developing means frame, and frame lid, of the cartridge in the preferred embodiment of the present invention, describing how they are joined.

[0034]FIG. 18 is a drawing for describing how the toner sealing member is joined with the toner storage-developing means frame.

[0035]FIG. 19 is an exploded perspective view of the development unit of the process cartridge in accordance with the present invention.

[0036]FIG. 20 is a perspective view of the development unit in FIG. 19.

[0037]FIG. 21 is a drawing for describing how the cleaning members of the process cartridge in accordance with the present invention are attached.

[0038]FIG. 22 is a schematic sectional view of an image forming apparatus, describing how the process cartridge is mounted into the image forming apparatus.

[0039]FIG. 23 is a schematic sectional view of the image forming apparatus, describing how the process cartridge is mounted into the image forming apparatus.

[0040]FIG. 24 is a perspective view of one of the cartridge guiding portions of the image forming apparatus in the preferred embodiment of the present invention.

[0041]FIG. 25 is a perspective view of the other cartridge guiding portion of the image forming apparatus, in the preferred embodiment of the present invention.

[0042]FIG. 26 is a drawing for describing how the process cartridge is accurately positioned relative to the image forming apparatus.

[0043]FIG. 27 is a drawing for describing how the process cartridge is accurately positioned relative to the image forming apparatus.

[0044]FIG. 28 is a drawing for describing how the process cartridge is accurately positioned relative to the image forming apparatus.

[0045]FIG. 29 is a schematic drawing of one of the modifications of the contact portions of the process cartridge in accordance with the present invention.

[0046]FIG. 30 is a schematic drawing of another modification of the contact portion of the process cartridge in accordance with the present invention.

[0047]FIG. 31 is a perspective view of a process cartridge in accordance with the prior arts.

[0048]FIG. 32 is a perspective view of one of the cartridge guiding portions of an image forming apparatus in accordance with the prior arts.

[0049]FIG. 33 is a schematic sectional view of an image forming apparatus in accordance with the prior arts, which is properly holding the process cartridge in accordance with the prior arts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Hereinafter, a combination of a process cartridge and an electrophotographic image forming apparatus, in accordance with the present invention, will be described in more detail with reference to the appended drawings.

[0051] In the following description of the present invention, the lengthwise direction of a process cartridge means the direction intersectional (roughly perpendicular) to the direction in which a process cartridge is mounted into, or removed from, the main assembly of an image forming apparatus. It is parallel to the surface of recording medium, and is intersectional (roughly perpendicular) to the direction in which the recording medium is conveyed. The right or left direction means the right or left direction of the recording medium as the recording medium is seen from the rear side in terms of the recording medium conveyance direction. The top surface of a process cartridge means the surface of the process cartridge which will be on the top side after the proper mounting of the process cartridge in the main assembly of an image forming apparatus, and the bottom surface of the process cartridge means the surface of the process cartridge which will be on the bottom side after the proper mounting of the process cartridge in the apparatus main assembly.

[0052]FIG. 1 shows one of the preferred embodiments of an electrophotographic image forming apparatus in accordance with the present invention. In this embodiment, a process cartridge B shown in FIG. 2 is removably mountable in this electrophotographic image forming apparatus. FIG. 1 is a schematic drawing for describing the structure of this electrophotographic image forming apparatus, which is properly holding the process cartridge B in FIG. 2. FIG. 2 is a schematic drawing for describing the structure of the process cartridge B.

[0053] As for the order of description, the general structure of the process cartridge B and the general structure of the electrophotographic image forming apparatus employing the process cartridge B will be first described. Then, the structure of the mechanism of the image forming apparatus main assembly for guiding the process cartridge B when the process cartridge B is mounted into, or removed from, the main assembly of the electrophotographic image forming apparatus will be described.

[0054] (General Structure)

[0055] Referring to FIG. 1, the electrophotographic image forming apparatus A (which hereinafter will be referred to simply as “image forming apparatus”) in this embodiment is a laser beam printer, and has an electrophotographic photoconductive member 7 in the form of a drum (which hereinafter will be referred to simply as “photoconductive drum”), as an image bearing member, which comprises an aluminum cylinder, and a photoconductive layer, that is, a layer of organic photoconductive substance, coated on the entirety of the peripheral surface of the aluminum cylinder.

[0056] A beam of light carrying image formation information is projected onto the photoconductive drum 7 from an optical system 1, forming a latent image on the photoconductive drum 7. This latent image is developed into a toner image with the use of developer (which hereinafter may be referred to as “toner”).

[0057] In synchronism with the formation of the toner image, a single or plurality of sheets of recording medium 2 in the sheet feeder cassette 3 a are fed one by one into the apparatus main assembly by the combination of a pickup roller 3 b, and a pressing member 3 c kept pressed against the pickup roller 3 b, and are conveyed further inward by a conveying means 3 f.

[0058] The toner image formed on the photoconductive drum 7 in the process cartridge B is transferred onto the recording medium 2 by applying voltage to a transfer roller 4 as a transferring means. Then, the recording medium 2 is conveyed to a fixing means 5 by the conveying means 3 f.

[0059] The fixing means 5 comprises: a driving roller 5 a, a heater 5 b, a supporting member 5 c, and a rotational fixing member 5 d. The rotational fixing member 5 d is a cylinder formed of sheet of a certain substance, and is supported by the supporting member 5 c. The heater 5 b is in the hollow of the rotational fixing member 5 d. The fixing means 5 fixes the unfixed toner image on the recording medium 2 to the recording medium 2, by the application of heat and pressure to the recording medium 2 while the recording medium 2 is passed through the fixing means 5. After the fixation, the recording medium 2 is further conveyed and discharged into the delivery area 6, by a pair of discharge rollers 3 d.

[0060] (Process Cartridge)

[0061] On the other hand, the process cartridge B comprises an electrophotographic photoconductive member, and a minimum of one processing means. As for the processing means, there are, for example, a charging means for charging the electrophotographic photoconductive member, and a developing means for developing a latent image formed on the electrophotographic member.

[0062] Referring to FIGS. 1 and 2, the process cartridge B in this embodiment comprises the photoconductive drum 7, as in electrophotographic photoconductive drum, having a photoconductive layer, a charge roller 8 as a charging means, a developing means 10, and an exposure opening 9. In operation, while the photoconductive drum 7 is rotated, the peripheral surface of the photoconductive drum 7 is uniformly charged by the application of voltage to the charge roller 8, and the uniformly charged portion of the peripheral surface of the photoconductive drum 7 is exposed to an optical image projected from the optical system 1, forming a latent image. Then, the latent image is developed by the developing means 10.

[0063] The developing means 10 in this embodiment comprises a toner storage-developing means frame 10 f 1, a frame lid 10 f 2, a rotational toner conveyance roller 10 b as a toner conveying means, a development roller 10 d (in which a magnet 10 c is stationarily disposed) as a rotational developing member, and a development blade 10 e. The toner storage-developing means frame 10 f 1 and frame lid 10 f 2 are joined, creating a toner chamber (toner storage) 10 a in which toner (magnetic single-component developer) is stored, and a development chamber 10 i. In operation, the toner in the toner chamber 10 a is sent out into the development chamber 10 i through the opening (toner passage) 10 k of the toner storage-developing means frame 10 f 1, by the toner conveyance roller 10 b. In the development chamber 10 i, the development roller 10 d is rotated, and a layer of triboelectrically charged toner is formed on the peripheral surface of the rotating development roller 10 d. Then, the toner is transferred onto the peripheral surface of the photoconductive drum 7 from the toner layer on the development roller 10 d, in the pattern of the latent image on the photoconductive drum 7, developing the latent image into a visual image, that is, a toner image.

[0064] Next, the toner image is transferred onto the recording medium 2 by the application of a voltage, opposite in polarity to the toner image, to a transfer roller 4. The transfer residual toner, that is, the toner remaining on the photoconductive drum 7 after the toner image transfer, is recovered during the following rotational cycle of the photoconductive drum 7. More specifically, during the following rotational cycle of the photoconductive drum 7, the peripheral surface of the photoconductive drum 7 is charged by the charge roller 8 with the presence of the transfer residual toner on the peripheral surface of the photoconductive drum 7, and another latent image is formed on the peripheral surface of the photoconductive drum 7 by exposure, and then, the residual toner from the preceding rotational cycle of the photoconductive drum 7 is recovered by the fog prevention bias (difference Vback between the potential level of the DC voltage applied to the developing apparatus and the surface potential level of the photoconductive member) during the development of the latent image. In this embodiment, a cleaning means such as a cleaning blade for removing the transfer residual toner on the photoconductive drum 7 is not provided.

[0065] The process cartridge B, which will be described in more detail later, is removably mounted into the cartridge mounting portion of the main portion, that is, the main assembly A0, of the image forming apparatus A, while being guided by the pair of guiding portions of the process cartridge B, which are located at the lengthwise ends of the process cartridge B, one for one.

[0066] The process cartridge B comprises a drum holding frame 102, which is one of the main sections of the cartridge frame, and the toner storage-developing means frame 10 f 1, which constitutes another of the main sections of the cartridge frame. The drum holding frame 102 and toner storage-developing means frame 10 f 1 are joined to form a drum frame unit C and a development unit D.

[0067] (Drum Frame Unit C)

[0068] Referring to FIGS. 3-7, the drum frame unit C, and the various members, for example, the photoconductive drum 7, charge roller 8, etc., making up the drum frame unit C, will be described.

[0069] Photoconductive Drum 7

[0070] Referring to FIGS. 5 and 6, the photoconductive drum 7 is provided with a drum gear 7 a, which is solidly attached to one of the lengthwise ends of the photoconductive drum 7. The drum gear 7 a comprises a triangular coupling portion 7 a 1, a first helical gear portion 7 a 2, and a second helical gear portion 7 a 3. The triangular coupling portion 7 a 1 is a driving force receiving portion by which the driving force from the image forming apparatus main assembly A0 is received, and is in the form of a twisted triangular pillar. The first helical gear portion 7 a 2 is a driving force transmitting portion by which the driving force is transmitted to the charge roller 8. The second helical gear portion 7 a 3 is a driving force transmitting portion by which the driving force is transmitted to the development unit D. Although not shown, to the other lengthwise end of the photoconductive drum 7, a flange is fixed, and to the flange, an electrode for grounding the photoconductive drum 7 is integrally attached.

[0071] The photoconductive drum 7, charge roller 8, etc., are internally held by the drum supporting frame 102. More specifically, one end of the photoconductive drum 7, from which the driving force is transmitted to the photoconductive drum 7, is rotatably supported by the drum holding frame 102, with the interposition of a side holder 107 integrally comprising a drum bearing 107 b, and the other end of the photoconductive drum 7 is rotatably supported by the drum holding frame 102, with the interposition of the drum supporting shaft 100. The diameter of the photoconductive drum 7 is in a range from 20 mm to 40 mm.

[0072] The second helical gear portion 7 a 3 of the drum gear 7 a is located close to one of a pair of spacer rings 10 m which determine the distance between the axes of the development roller 10 d and photoconductive drum 7. Therefore, the positional relationship, in terms of pitch circle, between the second helical gear portion 7 a 3 and development roller gear 10 n is precisely maintained.

[0073] Charge Roller 8

[0074] The charge roller 8 comprises a shaft 8 b, and a contact portion 8 a. The contact portion 8 a is placed in contact with the photoconductive drum 7, and is an elastic member formed on the peripheral surface of the shaft 8 b in a manner to wrap the shaft 8 b. The measurement of the shaft 8 b in its axial direction is greater than the measurement of the contact portion 8 a in its axial direction, extending beyond both ends of the contact member 8 a. The two portions extending from two ends of the contact portion 8 a, one for one, will be referred to as shaft portions 8 b 1 and 8 b 2. The shaft 8 b and contact portion 8 a constitute integral parts of the charge roller 8. The diameter of the charge roller 8 is in a range of 8-20 mm.

[0075] Between the peripheral surface of the photoconductive drum 7 and the peripheral surface of the contact portion 8 a of the charge roller 8, a layer of electrically conductive microscopic particles is present. The electrical conductive microscopic particles used in this embodiment are microscopic zinc oxide particles (having a resistance of 1.500 Ω·cm, and a permeability of 35%). They are formed by air-classifying the particles (secondary particles) created by applying pressure to particles (primary particles) of zinc oxide, the diameters of which are in a range of 0.1-0.3 μm. They are 1.5 μm in volume average particle diameter. In terms of particle size distribution, the particles no more than 0.5 μm in size constitute 35% of the volume, and particles no less than 5 μm in size constitute zero to several percentages of the volume.

[0076] Charge Roller Bearing 103

[0077] The shaft portions 8 b 1 and 8 b 2 of the charge roller 8 are fitted with charge roller bearings 103 b and 103 a, respectively, which are roughly C-shaped in cross section, and which are in contact with the shaft portions 8 b 1 and 8 b 2, respectively, by their internal surface, with respect to their C-shaped cross sections.

[0078] Further, the charge roller bearings 103 a and 103 b each have a locking portion (unshown) which engages with a part of the drum supporting frame 102 in such a manner that enables the assembly comprising the charge roller 8 and charge roller bearings 103 to move relative to the photoconductive drum 7.

[0079] Compression Coil Spring 104

[0080] Between the drum supporting frame 102 and the pair of charge roller bearings 103 a and 103 b, a pair of compression coil springs 104, as elastic members, are disposed, one for one. One end of the lengthwise ends of each compression coil spring 104 is fitted around the spring holder portion of the corresponding charge roller hearing 103 a (103 b), and the other end is fitted around the corresponding spring holder portion of the drum supporting frame 102. The charge roller 8 is kept pressed on the peripheral surface of the photoconductive drum 7 by these compression coil springs 104.

[0081] More specifically, in order to keep the theoretical amount of the penetration of the charge roller 8 into the photoconductive drum 7 at 0.2 mm, a pair of compression springs, each of which exerts an operational load of 340 gf are disposed on the left and right sides, one for one. The spring constant of each compression coil spring 104 is equivalent to a compression amount of approximately 3 mm.

[0082] In this embodiment, the theoretical amount of the penetration of the charge roller 8 into the photoconductive drum 7 is controlled only by controlling the amount of the pressure applied by the pair of compression coil springs 104.

[0083] (Structure of Charge Roller Driving Mechanism)

[0084] Referring to FIGS. 5-12, the structure of the mechanism for driving the charge roller 8 will be described. FIGS. 7-12 describe the gear train of the process cartridge.

[0085] Drum Gear 7 a

[0086] Referring to FIG. 11, the photoconductive drum 7 in this embodiment comprises the drum cylinder 7A and the photoconductive layer coated on the entirety of the peripheral surface of the drum cylinder 7A. To one end of the drum cylinder 7A, a drum gear 7 a is solidly attached. The drum gear 7 a transmits the rotational driving force to the charge roller 8, and also to the transfer roller 4 and development roller 10 d.

[0087] The drum gear 7 a is solidly attached to one end of the drum cylinder 7A, as described above, and its axial line coincides with that of the drum cylinder 7A. The drum gear 7 a comprises the helical gear portions 7 a 2 and 7 a 3, and a shaft portion 7 a 4. The helical gear portions 7 a 2 and 7 a 3 are the gear proper portions of the drum gear 7 a, and are on the outward side of the drum cylinder 7A in terms of the axial direction of the drum cylinder 7A. The shaft portion 7 a 4 constitutes the center portion of the drum gear 7 a, and which overlaps the helical gear portions 7 a 2 and 7 a 3, in terms of the radius direction of the drum gear 7 a. In other words, the helical gear portions 7 a 2 and 7 a 3 are cylindrical, and the shaft portion 7 a 4 is extended in the holes of the cylindrical helical gear portions 7 a 2 and 7 a 3, with its axial line coinciding with those of the cylindrical helical gear portions 7 a 2 and 7 a 3.

[0088] Thus, there is a cylindrical gap 7 a 5 between the peripheral surface of the shaft portion 7 a 4 and the internal surfaces of the cylindrical helical gear portions 7 a 2 and 7 a 3. This cylindrical space 7 a 5 constitutes the space into which the bearing portion 107 b of the side holder 107 fits as the photoconductive drum 7 is attached to the cartridge frame (drum holding frame 102), so that the shaft portion 7 a 4 is rotatably supported by the bearing portion 107 b.

[0089] The drum gear 7 a also comprises the triangular coupling portion 7 a 1, that is, a projection constituting the coupling means on the cartridge side, which projects from the outward end of the shaft portion 7 a 4. As the process cartridge B is mounted into the apparatus main assembly A0, this projection 7 a 1 engages with the coupling means of the apparatus main assembly, that is, a driving force transmitting member 200 (FIG. 24). More specifically, the driving force transmitting member 200 has a roughly triangular recess, and the projection 7 a 1 fits into this recess to receive the rotational driving force from the apparatus main assembly A0. The projection 7 a 1 is twisted around its rotational axis, and its cross section perpendicular to its rotational axis is polygonal. The recess of the driving force transmitting member 200 is twisted around the rotational axis of the driving force transmitting member 200, and its cross section perpendicular to the rotational axis of the driving force transmitting member 200 is polygonal.

[0090] The drum gear 7 a in this embodiment is structured so that the end surface of the shaft portion 7 a 4 is on the inward side by an amount of E relative to the outward end surface of the helical gear 7 a, more specifically, the end surface of the helical gear portion 7 a 2. Thus, the projection 7 a 1 partially overlaps the helical gear portion 7 a 2 in terms of the radius direction of the helical gear 7 a. With the provision of this structural arrangement, the drum gear 7 a in this embodiment is wider in terms of its axial direction, being therefore superior, in terms of physical strength as well as meshing ratio, than a drum gear in accordance with the prior arts. Thus, it is possible to an excellent image.

[0091] Also with the provision of the above described structural arrangement, the shaft portion 7 a 4 is rotationally supported by the bearing portion 107 b of the side holder 107, which is in the cylindrical space 7 a 5 between the peripheral surface of the shaft portion 7 a 4 and the inward surface of the cylindrical gear proper portions of the drum gear 7 a. Therefore, the repulsive force resulting from the meshing of the gears arc caught directly below the teeth of the gears, assuring that the repulsive force does not work in the direction to bend the photoconductive drum 7. Therefore, it is assured that the photoconductive drum 7 is rotationally driven in the preferable manner.

[0092] As described above, the drum gear 7 a in this embodiment has the first helical gear portion 7 a 2, which is on the outward side in terms of the lengthwise direction of the cylinder 7A, and the second helical gear portion 7 a 3, which is on the inward side. The first and second helical gear portions 7 a 2 and 7 a 3 are disposed next to each other, with their rotational axes coinciding. In terms of the diameter at the tooth tip (that is, diameter at root of gorge), the first helical gear portion 7 a 2 is smaller than the second helical gear portion 7 a 3. With the provision of this structural arrangement, the optimal number of teeth can be selected for the drum gear 7 a, in accordance with the optimal numbers of revolution of the development roller 10 d and charge roller 8.

[0093] In this embodiment, the first and second helical gear portions 7 a 2 and 7 a 3 are made different in the direction of twist. More specifically, as seen from the drum side, the first helical gear portion 7 a 2 is twisted rightward, whereas the second helical gear portion 7 a 3 is twisted leftward. Thus, as the photoconductive drum 7 in the process cartridge B in the image forming apparatus main assembly A0 is rotated, the first helical gear portion 7 a 2 pushes the gear, which is being driven by the helical gear portion 7 a 2, in the direction opposite to the location of the drum cylinder 7A, that is, inward of the process cartridge B, whereas the second helical gear portion 7 a 3 pushes the gear, which is being driven by the helical gear portion 7 a 3, in the direction opposite to the location of the helical gear 7 a, that is, outward direction of the process cartridge B.

[0094] Also in this embodiment, the gear portion 110 b of a geared coupler 110, which transmits the rotational driving force to the charge roller 8, is pushed in the direction opposite to the location of the gear portion 110 b In terms of the lengthwise direction of the charge roller 8, that is, inward of the process cartridge B indicated by an arrow mark in FIG. 11.

[0095] Idler Gear 111

[0096] An idler gear 111 is a step gear having two gear portions 111 a and 111 b different in diameter, and is rotationally supported by the shaft 102 c (FIG. 5) which is a part of the drum supporting frame 102. The end portion of the shaft 102 c is supported by the side holder 107, being prevented from being broken off by the force resulting from the driving of the idler gear 111 by the gear in mesh with the idler gear 111.

[0097] The two gear portions 111 a and 111 b of the idler gear 111 are in mesh with the gear portion 110 b of the geared coupler 110, and the first helical gear portion on 7 a 2 of the drum gear 7 a, respectively, and transmit the rotational driving force from the drum gear 7 a to the gear portion 110 b of the geared coupler 110.

[0098] Geared Coupler 110

[0099] The geared coupler 110 has the aforementioned gear portion 110 b, and the coupler proper portion 110 a integral with the gear portion 110 b. As will be evident from FIG. 9, the coupler proper portion 110 a of the geared coupler 110 is shaped like a pair of parallel cylinders connected by a roughly rectangular plate placed between their peripheral surfaces. The pair of the cylindrical portions of the coupler proper portion 110 a are symmetrical with respect to the rotational axis of the coupler proper portion 110 a. The gear portion 110 b of the geared coupler 110 meshes with the aforementioned idler gear 111 and transmits the rotational driving force.

[0100] As the rotational driving force is transmitted to the charge roller 8 through the geared coupler 110, the geared coupler 110 is subjected to the force generated in the direction perpendicular to the rotational axis of the geared coupler 110 by the idler gear 111 in mesh with the gear portion 110 b of the geared coupler 110. Thus, in order to minimize the effect of this force, it is desired that the geared coupler 110 is supported at both ends in terms of its axial direction. Therefore, the geared coupler 110 is provided with a shaft portion 110 c having a predetermined diameter. The shaft portion 110 c is between the coupler proper portion 110 a and gear portion 110 b, and its rotational axis coincides with that of the geared coupler 110. It is rotationally borne by the wall of a through hole 108 (FIG. 5) of the drum supporting frame 102. As the process cartridge B is driven, the gear portion 110 b is pushed inward of the process cartridge B, indicated by the arrow mark in FIG. 11, as described above. Therefore, while the process cartridge B is driven, the inward lateral surface of the gear portion 110 b of the geared coupler 110 remains in contact with the lip portion of the through hole 108, assuring that the charger roller 8 remains stable while it is rotationally driven.

[0101] Referring to FIG. 5, the geared coupler 110 is also provided with a hole 110 d with a predetermined diameter, which is located on the side opposite to the shaft portion 110 c in terms of the axial direction of the geared coupler 110. The geared coupler 110 is rotationally supported by the shaft portion 106 a of a supporting member 106, which is attached to the drum supporting frame 102, along with the side holder 107.

[0102] The geared coupler 110 couples with the first coupling portion 112 a of an intermediary coupler 112, and transmits the rotational driving force.

[0103] Intermediary Coupler 112

[0104]FIG. 8 is a sectional view of the coupled combination of the geared coupler 110, intermediary coupler 112, and coupler 109, describing how they are coupled. The drawing shows only the coupler proper portion 110 a of the geared coupler 110, and only the coupler proper portion 109 c of the coupler 109.

[0105] In FIG. 8. the coupler proper portion 110 a is hatched in order to differentiate the coupler proper portion 110 a from the coupler proper portion 109 c.

[0106] Referring to FIG. 9, the intermediary coupler 112 is sandwiched between the coupler 109 and geared coupler 110. The intermediary coupler has a second coupling portion 112 b, which is on coupler 109 side of the intermediary coupler 112, and a pair of first coupling portions 112 a, which is on the geared coupler 110 side. The second coupling portion 112 b is a hole elongated in the direction perpendicular to axial direction of the intermediary coupler 112, and into which the coupler proper portion 109 c fits. Each of the pair of first coupling portions 112 a is a hole open at the peripheral surface of the coupler 112 as well as one of the lateral surfaces of the coupler 112. Its bottom wall in terms of the radius direction of the coupler 112 is rounded, and its bottom wall in terms of the axial direction of the coupler 112 is flat. The pair of first coupling portions 112 a are where the pair of couplers proper portions 110 a of the geared coupler 110 fit one for one.

[0107] The first coupling portions 112 b in the form of an elongated hole is symmetrical with respect to the rotational axis of the intermediary coupler 112, and the pair of the first coupling portions 112 a in the form of a groove are symmetrically positioned relative to each other with respect to the axial line of the intermediary coupler 112. The first and second coupling portions 112 a and 112 b are positioned so that the center line of the first coupling portion 112 a parallel to the lengthwise direction of the first coupling portion 112 a, and the center line of each of the pair of second coupling portions 112 b parallel to the lengthwise direction of the second coupling portion 112 b, do not become parallel to each other, that is, the angle between them does not become zero; preferably, they are positioned so that the two lines become perpendicular to each other, as shown in FIG. 8.

[0108] Coupler 109

[0109] In order to receive the force for rotationally driving the charge roller 8, the charge roller 8 is provided with the coupler 109 as a driving force catching member, which is attached to one end of the shaft portion 8 b 1 of the charge roller 8. More specifically, one end of the shaft portion 8 b 1 of the charge roller 8 is given a D-shaped cross section, and is put through the D-shaped center hole of the coupler 109.

[0110] The coupler 109 has a pair of the couplers proper portions 109 c in the form of a cylindrical projection, which are symmetrically positioned relative to each other with respective to the axial line of the coupler 109. These couplers proper portions 109 c fit into the pair of second coupling portions 112 b of the intermediary coupler 112, one for one, and catch the rotational driving force.

[0111] The first coupling portion 112 a of the intermediary coupler 112 is in the form of an elongated hole. Therefore, while the intermediary coupler 112 and geared coupler 110 are in the properly coupled state, that is, while the projection 110 a is properly situated in the hole 112 a, there is a certain amount of play between the end surface of the coupling portion 112 a and the peripheral surface of the corresponding projection 110 a, in terms of the lengthwise direction of the coupling portion 112 a, allowing the projection 110 a to slide in the lengthwise direction of the coupling portion 112 a.

[0112] Further, the pair of second coupling portions 112 b are in the form of a groove with an open end extending in the radius direction of the coupler 112. Therefore, while the intermediary coupler 112 and coupler 109 are in the properly coupled state, in other words, while each projection 109 c is properly situated in the corresponding hole 112 b, there is a certain amount of play between the internal surface of the hole 112 b and the peripheral surface of the corresponding projection 109 c, allowing the projection 109 c to slide in the lengthwise direction of the hole 112 b.

[0113] As described above, the charge roller 8 is rotated in such a direction that in the contact area between the charge roller 8 and photoconductive drum 7, the peripheral surface of the charge roller 8 moves in the direction opposite to the direction in which the peripheral surface of the photoconductive drum 7 moves. Therefore they rub against each other, increasing the frequency at which a given point of the peripheral surface of the charge roller 8 (photoconductive drum 7) comes into contact with the peripheral surface of the photoconductive drum 7 (charge roller 8).

[0114] (Structure of Mechanism for Driving Development Roller 10 d, Transfer Roller 4, and Toner Conveyance Roller 10 b)

[0115] As described above, the drum gear 7 a drives the charge roller 8 with the interposition of the idler gear 111 and geared coupler 110. It also drives the development roller 10, transfer roller 4, and toner conveying member (conveyance roller) 10 b, as shown in FIG. 10.

[0116] As described above, the first helical gear portion 7 a 2 is indirectly in mesh, with the interposition of the idler gear 111, with the gear portion 110 b of the geared coupler 110 attached to one end of the shaft of the charge roller 8, and transmits the rotational driving force to the charge roller 8. Further, the first helical gear portion 7 a 2 is meshes with a gear 4 a attached to one end of the shaft of the transfer roller 4, and transmits the rotational driving force to the transfer roller 4 at the same time as it transmits the rotational driving force to the charge roller 8.

[0117] The second helical gear portion 7 a 3 of the drum gear 7 a is in mesh with the gear 10 n attached to one end of the shaft of the development roller 10 d, and rotationally drives the development roller 10 d. Further, the gear 10 n of the development roller 10 d is indirectly in mesh, with the interposition of an idler gear 10 t, that is, a step gear, and an idler gear 10 u, that is, a step gear, with a gear 10 v attached to one end of the conveyance roller 10 b, and transmits the rotational driving force to the conveyance roller 10 b.

[0118] In this embodiment, the drum gear 7 a has the first and second helical gear portions 7 a 2 and 7 a 3, which are different in the direction in which their teeth are twisted, as described above. The development roller 10 d has the development roller gear 10 n attached to one end of the development roller 10 d. This development roller gear 10 n is in mesh with the second helical gear portion 7 a 3 of the drum gear 7 a, and is rotationally driven by the drum gear 7 a, as described above.

[0119] The transfer roller 4 has the transfer roller gear 4 a attached to one end of the transfer roller 4. This transfer roller gear 7 a is in mesh with the first helical gear portion 7 a 2 of the drum gear 7 a, and is rotationally driven by the drum gear 7 a.

[0120] For the improvement of positional accuracy, the first helical gear portion 7 a 2 of the drum gear 7 a in this embodiment is twisted in the direction to push the development roller 10 d in the outward direction indicated by an arrow mark in FIG. 11, whereas the second helical gear portion 7 a 3 of the drum gear 7 a is twisted in the direction to push the charge roller 8 and transfer roller 4 in the inward direction indicated by the arrow mark in FIG. 11 as described above.

[0121] Further, due to the structural constraint of the gear driving apparatus, the second helical gear portion 7 a 3 of the drum gear 7 a is smaller in width in terms of its axial direction than the first helical gear portion 7 a 2 of the drum gear 7 a.

[0122] Also in this embodiment, the second helical gear portion 7 a 3 of the drum gear 7 a is made larger in pitch circle diameter than the first drum gear 7 a 2 of the drum gear 7 a.

[0123] In this embodiment, the diameter of the photoconductive drum 7 is 24 mm, and the diameter of the charge roller 8 is 18 mm. Further, the diameter of the development roller 10 d is 12 mm.

[0124] Also in this embodiment, the peripheral velocity of the development roller 10 d is roughly 118% of that of the photoconductive drum 7, and the peripheral velocity of the charge roller 8 is roughly 80% of that of the photoconductive drum 7.

[0125] Also in this embodiment, the charge roller 8 is rotated in such a direction that in the contact area between the photoconductive drum 7 and charge roller 8, the peripheral surface of the charge roller 8 moves in the direction opposite to the direction in which the peripheral surface of the photoconductive drum 7 moves, and the development roller 10 d is rotated in such a direction that in the area in which the peripheral surfaces of the photoconductive drum 7 and development roller 10 d are closest to each other, the peripheral surfaces of the photoconductive drum 7 and development roller 10 d move in the same direction. In other words, the photoconductive drum 7 and charge roller 8 rotate in the clockwise direction, and the development roller 10 d rotates in the counterclockwise direction, as shown in FIG. 1. Further, the conveyance roller 10 b is rotated in the clockwise direction.

[0126] Next, referring to FIGS. 13-15, another example of a gear train in accordance with the present invention will be described.

[0127] The helical drum gear 7 a of the gear train shown in FIGS. 10-12 has the first helical gear portion 7 a 2, which is on the outward side in terms of the lengthwise direction of the cylinder 7A, and the second helical gear portion 7 a 3, which is on the inward side. In comparison, the helical gear 7 a of the gear train shown in FIGS. 13-15 has only one gear portion (similar to helical gear portion 7 a 2), which plays both the role played by the first helical gear portion 7 a 2 of the drum gear 7 a of the gear train shown in FIGS. 10-12, and the role played by the second helical gear portion 7 a 3 of the drum gear 7 a shown in FIGS. 10-12.

[0128] Also in the case of the example of a gear train in accordance with the present invention, shown in FIGS. 13-15, the drum gear 7 a is in mesh with the idler gear 111, gear 4 a, and gear 10 n; the outward side of the drum gear 7 a, in terms of its axial direction, is in mesh with the idler gear 111 and gear 4 a, and the inward side of the drum gear 7 a is in mesh with the gear 10 n.

[0129] The gear train in shown in FIGS. 10-12, and the gear train shown in FIGS. 13-15 are virtually the same in structure, except for the structure of the drum gear 7 a. Therefore, the components, members, portions, etc., of the former, which are the same as the counterparts in the latter, are given the identical referential numerals, and they will not be described here.

[0130] Next, the structure of the gear train, shown in FIGS. 13-15, for driving the charge roller 8, transfer roller 4, development roller 10 d, etc., will be described in comparison to the gear train shown in FIGS. 10-12.

[0131] (Structure of Side Holder)

[0132] Referring to FIGS. 5-7, the structure of the side holder 107 will be described.

[0133] As described before, the side holder 107 has: a hole 107 a for the reinforcement of the shaft 102 for supporting the idler gear 111; a bearing portion 107 b for rotationally bearing the photoconductive drum 7; and a coupler of joggles 107 h and 107 i for precisely positioning the side holder 107 relative to the drum holding frame 102.

[0134] Further, the side holder 107 has a through hole 107 c (FIG. 5), through which an assembly tool for aligning the teeth of the drum gear 7 a and the teeth of the idler gear 111 is inserted into the internal space of the side holder 107, in order to mesh the drum gear 7 a and idler gear 111 during the process cartridge assembly.

[0135] (Assembly of Process Cartridge)

[0136] Method for Assembling Drum Supporting Frame Unit C

[0137] Referring again to FIG. 5, the assembling of the drum supporting frame unit C will be described.

[0138] First, an electrical contact member 133 for supplying the charge roller 8 with bias, and a couple of drum end cleaning members 114 (114 a and 114 b), are attached to the drum supporting frame 102. The cleaning members 114 will be described later in detail.

[0139] As described before, the shaft portions 8 b 1 and 8 b 2 of the charge roller 8 are rotationally borne by the bearing 103 a and 103 b engaged with the lengthwise end portions of the drum supporting frame 102. More specifically, the shaft portion 8 b 2, that is, the shaft portion on the electrical contact member 113 side, is fitted with the bearing 103 a formed of electrically conductive plastic, and the bearing 103 a is attached to a predetermined portion of the drum supporting frame 102, with the interposition or a spring 104 for keeping the charge roller 8 pressed upon the photoconductive drum 7. The shaft portion 8 b, that is, the shaft portion on the side with no electrical contact member, is fitted with the bearing 103 b formed of plastic, and the bearing 103 b is attached to another predetermined portion of the drum supporting frame 102, with the interposition of the spring 104 for keeping the charge roller 8 pressed upon the photoconductive drum 7.

[0140] Next, one end of the shaft 8 b 1 of the charge roller 8 is fitted with the aforementioned coupler 109 and intermediary coupler 112 in this order. Then, the end of the charge roller 8 with the electrical contact member 113 is fitted with the bearing 103 a, and the end of the charge roller 8 with no electrical contact member is fitted with the bearing 103 b. The charge roller 8 is coated in advance with the aforementioned electrically conductive microscopic particles.

[0141] The geared coupler 110 is fitted into the hole 108 of the drum supporting frame 102, with the coupling portion of the geared coupler 110 aligned with the elongated hole of the intermediary coupler 112.

[0142] The idler gear 111 is fitted around the supporting shaft 102 c of the drum supporting frame 102, while being meshed with the gear portion 110 b of the geared coupler 110.

[0143] The supporting member 106 is attached to the drum supporting frame 102, while inserting the shaft portion 106 a of the supporting member 106 into the hole 110 d of the geared coupler 110, being therefore precisely positioned relative to the drum supporting frame 102.

[0144] The photoconductive drum 7 is precisely positioned relative to the drum supporting frame 102 with the use of a tool. Then, from the side opposite to the side with the drum gear, the drum supporting shaft 100 is put through the hole 102 a of the drum supporting frame 102, and the flange of the photoconductive drum 7, solidly fixing the drum supporting shaft 100 to the drum supporting frame 102, and rotationally supporting the photoconductive drum 7. On the drum gear side, the side holder 107 is attached to the drum supporting frame 102, precisely positioning the side holder 107 relative to the drum supporting frame 102, while fitting the projection 7 a 1 of the drum gear 7 a into the hole 107 b of the side holder, and the bearing portion 107 b into the cylindrical space 7 a 5 or the drum gear 7 a. During this process, a tool for rotating the idler gear 111 is inserted through the through hole 107 c of the side holder 107, and the side holder 107 is solidly fixed to the drum supporting frame 102 with the use of small screws, while rotating the idler gear 111 by the inserted tool so that the first helical gear portion 7 a 2 smoothly meshes with the idler gear 111.

[0145] The above described processes complete the drum frame unit C.

[0146] (Method for Assembling Developing Means 10 and Development Unit D)

[0147] Next, referring to FIG. 2, and FIGS. 16-20, the development unit D and developing means 10 of the process cartridge B will be described in detail.

[0148] Referring to FIGS. 2 and 17, the developing means 10 comprises the toner storage-developing means frame 10 f 1 and frame lid 10 f 2, which are joined to create the toner chamber (toner storage portion) 10 a and development chamber 10 i.

[0149] The toner storage-developing means frame 10 f 1 is provided with the opening 10 k which the toner in the toner chamber 10 a passes when it is supplied to the development roller 10 d.

[0150] Referring to FIG. 16, when the process cartridge B is brand-new, the toner passage opening 10 k of toner storage-developing means frame 10 f 1 of the process cartridge B is blocked with a multilayer toner sealing member 27 having a cover film portion 27 b thermally welded to the seal attachment portion of the toner storage-developing means frame 10 f 1, with the use of laser light. The cover film portion 27 b is provided with a thermally weldable layer 31 for fixing the toner sealing member 27. The details of the structure of the toner sealing member 27 are well known to the people in this business, and are disclosed in, for example, Japanese Laid-open Patent Application 11-102105, etc. Thus, for the details, this patent application or the like should be referred to.

[0151] Referring to FIG. 18, the toner sealing member 27 is pasted to the seal attachment portion 10 h, which extends along the four edges of the aforementioned toner passage opening 10 k. In order to unseal the toner passage opening 10 k, the toner scaling member 27 is precut by a laser to a depth of half its thickness, as described above (Japanese Laid-open Patent Application 11-102105). e

[0152] One lengthwise end of the toner storage-developing means frame 10 f 1 is provided with a toner inlet (unshown), that is, an opening, through which the toner chamber 10 a is filled with toner, and which is sealed with a cap 10 j (FIG. 19) after the filling of the toner chamber 10 a with toner.

[0153] Next, referring to FIGS. 18 and 19, the process for assembling the development unit D will be described.

[0154] In order to assembly the developing means 10, first, an end seal 10 r for preventing the toner from leaking from the lengthwise ends of the development roller 10 d, a sealing member 10 s for preventing toner from leaking from the lengthwise ends of the development blade 10 e, and a sheet-like member 10 t for preventing toner from scattering from the gap under the development roller 10 d, are pasted to the toner storage-developing means frame 10 f 1 and frame lid 10 f 2, with the use of double-sided adhesive tape, or the like.

[0155] The development blade 10 e is solidly fixed to the toner storage-developing means frame 10 f 1, by the lengthwise ends of the metallic plate portion 10 e 1 of the development blade 10 e, with the use of small screws.

[0156] One (on the left side in FIG. 19) of the two end members (holding members) 10 g covers the gear train comprising: the development roller gear 10 n (FIGS. 10 and 11) solidly fixed to one end of the development roller 10 d and in mesh with the first helical gear portion 7 a 2 of the drum gear 7 a (FIG. 5) solidly fixed to one end of the photoconductive drum 7; and the two idler gears 10 u and 10 t for transmitting the driving force from the development roller gear 10 n to the conveyance gear (unshown) of the toner conveyance member 10 b. The other end member log (on the right side in FIG. 19) is provided with a hard tab 10 g 1, which will be described later.

[0157] The extended tab portion 27 a (FIG. 16) of the toner sealing member 27 is folded back at one end 10 p (FIG. 18) of the toner passage opening 10 k, all the way to the other end of the toner passage opening 10 k, and is extended outward through the hole 10 f 11 (FIG. 19) of the toner storage-developing means frame 10 f 1.

[0158] The tab proper portion 27 a 1 of the extended tab portion 27 a of the toner sealing member 27 is further extended outward through the hole 10 g 6 of the end member 10 g, and the through hole 10 g 4 of the hard tab 10 g 1, so that the surface R (surface coated with sealant layer 31) of the extended tab portion 27 a, shown in FIG. 16, thermally fixable to the hard tab 10 g 1 faces the handle 10 g 1. The end of the tab proper portion 27 a 1 is thermally fixed to a predetermined area of the hard tab 10 g 1 (FIG. 19).

[0159] The hard tab 10 g 1 is an integral part of the end member 10 g, and is formed so that it can be easily torn off from the end member 10 g. More specifically, the portion by which the hard tab 10 g 1 is connected to the man structure of the end member 10 g is made very thin so that the hard tab 10 g 1 can be easily separated from the main structure by bending.

[0160] The hard tab 10 g 1 is integrally formed with the end member 10 g. Preferably, it is formed of high impact polystyrene (HIPS), acrylonitrile-butadiene polymer (ABS), etc., that is, copolymers containing styrene. The end portion 27 a 1, or tab proper, of the extended tab portion 27 a is thermally welded to the hard tab 10 g 1.

[0161] The above described processes complete the development unit D shown in FIG. 20.

[0162] Referring to FIG. 19, the end member 10 g is provided with an arm-like portion 10 g 7, which protrudes toward the drum supporting frame 102. The arm-like portion 10 g 7 has a hole 10 g 8, which is in the end portion of the arm-like portion 10 g 7, extending in the lengthwise direction of the process cartridge B. The drum supporting frame 102 and the end member 10 g can be joined by putting a pin (unshown) through the hole 10 g 8 of the arm-like portion of the end member 10 g, and the unshown hole of the drum supporting frame 102, so that they can be rotated about the pin. The arm-like portion 10 g 7 is also provided with a spring holding portion 10 g 9, which protrudes from the top surface of the arm-like portion 10 g 7, and a compression coil spring is placed in the compressed state between the arm-like portion 10 g 7 and drum supporting frame 102, with one end of the compression coil spring fitted around the spring holding portion 10 g 9. The end portion of the development roller 10 d are fitted with a gap maintaining members (spacer) 10 m (10 m 1 and 10 m 2), one for one, and the spacers 10 m are pressed on the peripheral surface of the photoconductive drum 7. Therefore, a predetermined distance is kept between the peripheral surfaces of the development roller 10 d and photoconductive drum 7.

[0163] Referring to FIGS. 19 and 21, in this embodiment, the spacer 10 m is in the form of a cap, and each end of the development roller 10 d is fitted with the cap-like spacer 10 m. The center portion of the peripheral surface of the cap-like spacer 10 m, in terms of its axial direction, having a predetermined width, is raised in relation to adjacent portions of the peripheral surfaces, and, this portion is pressed on the peripheral surface of the photoconductive drum 7.

[0164] The development unit D and drum frame unit C are joined, as described above, to complete the process cartridge B.

[0165] (Structure of Cleaning Member 114)

[0166] While a toner image is transferred from the photoconductive drum 7 onto the recording medium 2, and/or while the recording medium 2 bearing the unfixed transferred image is conveyed to the fixing means 5 and enters the fixing means 5, toner particles sometimes floats in the image forming apparatus main assembly, although by only a very small amount.

[0167] Some of the floating toner particles adhere to the photoconductive drum 7, even across the portion corresponding in position to the cap-like roller 10 m. As the toner particles adhere to the portion of the photoconductive drum 7 corresponding to the cap-like roller 10 m, they are compressed onto the peripheral surface of the photoconductive drum 7 by the cap-like roller 10 m, being sometimes semipermanently adhered in the agglomerated form to the peripheral surface or the photoconductive drum 7, because the cap-like roller 10 m is kept pressed upon the peripheral surface of the photoconductive drum 7 by the force from the aforementioned springs. Some of the agglomerations of toner particles remain on the portion of the photoconductive drum 7 corresponding to the cap-like roller 10 m, and gradually grow, until the service life of the process cartridge expires.

[0168] The presence of the above described agglomerations of toner particles on the portion of the peripheral surface of the photoconductive drum 7 corresponding to the cap-like roller 10 m changes the distance between the photoconductive drum 7 and development roller 10 d, negatively affecting the development of the latent image on the photoconductive drum 7. Further, as the development roller 10 d rides over the agglomerations of toner particles, vibrations occur, presenting a possibility that an image defect that the pitch in terms of the direction perpendicular to the direction in which the recording medium 2 is conveyed is randomly disturbed.

[0169] In this embodiment, therefore, in order to remove the toner particles adhering to the end portions of the photoconductive drum 7 which the corresponding cap-like rollers 10 contact, one-piece cleaning members 114 (114 a and 114 b) are attached to the end portions of the drum supporting frame 102, one for one, with the use of double-sided adhesive tape, in such a manner that the cleaning members 114 contact the peripheral surfaces of the right and left lengthwise ends of the photoconductive drum 7, one for one.

[0170] As for the preferable materials for the cleaning member 114, there are:

[0171] (1) laminar combination of an elastic layer, for example, a layer or foamed polyurethane or felt, and a layer of nonwoven fabric fixed to thereto;

[0172] (2) laminar combination of an elastic layer, for example, a layer of foamed polyurethane or felt, and a layer of felt, as toner removing layer, fixed thereto;

[0173] (3) laminar combination of an elastic layer, for example, a layer of foamed polyurethane or felt, and a layer of pile fixed thereto;

[0174] (4) combination of foamed urethane, and high density polyurethane fixed thereto;

[0175] (5) felt;

[0176] (6) foamed polyurethane; or

[0177] (7) nonwoven fabric. When the laminar materials such as the above (1), (2), or (3), are used as the material for the cleaning member 114, the cleaning member 114 is disposed so that the nonwoven fabric, felt layer as the toner removing layer, or pile, is placed in contact with the photoconductive drum 7.

[0178] These cleaning members 114 are capable of reliably taking into the nonwoven fabric portion or the like, the stray toner particles having adhered to the peripheral surface of the photoconductive drum 7, without causing the stray toner particles to fall within the apparatus main assembly; in other words, they can remove the stray toner particles on the photoconductive drum 7 in a preferable manner, reducing frictional resistance as much as possible, preventing thereby the increase in the driving force (rotational driving force) necessary to rotate the photoconductive drum 7.

[0179] Next, referring to FIG. 21, the positional relationships between the above described cleaning member 114 attached to the drum supporting frame 102, and the photoconductive drum 7, and between the cleaning member 114 and charge roller 8, will be described.

[0180] The adhesion of the stray toner particles such as the above described floating toner particles to the portions of the photoconductive drum 7, outside the changing range of the charge roller 8, that is, the portions of the photoconductive drum 7 extending outward beyond the ends of the charge roller 8, may result in the contamination of the image edges and/or recording medium edges by the stray toner particles.

[0181] Referring to FIG. 21, in this embodiment, each end of the development roller 10 d is capped with the cap-like roller 10 m (10 m 1 and 10 m 2) as a spacer, the raised center portion 10 m 3 of which is kept pressed on the peripheral surface of the photoconductive drum 7. The cleaning members 114 (114 a and 114 b) are disposed in alignment with the cap-like rollers 10 m (10 m 1 and 10 m 2), respectively, in terms of the direction perpendicular to the axial direction of the photoconductive drum 7 (charge roller 8, development roller 10 d), with the presence of a gap between the cleaning member 114 and corresponding cap-like member 10 m.

[0182] In other words, referring to FIGS. 5 and 21, in terms of the lengthwise direction of the photoconductive drum 7, the range Ca, across which the raised center portion of the cap-like roller 10 m 1 as a spacer, of the development roller 10 d, is in contact with the left end portion of the peripheral surface of the photoconductive drum 7, falls within the range of the first cleaning member 114 a disposed in contact with the left end portion of the peripheral surface of the photoconductive drum 7. Further, the inward edge 114 a 1 of the first cleaning member 114 a is outside the range Ld, in terms of the lengthwise direction of the photoconductive drum 7, across which the development process is carried out by the development roller 10 d, and inside the range Lc, across which the charge roller 8 is in contact with the photoconductive drum 7.

[0183] Also referring to FIGS. 5 and 21, similarly, in terms of the lengthwise direction of the photoconductive drum 7, the range Cb, across which the raised center portion of the cap-like roller 10 m 2, as a spacer, of the development roller 10 d, is in contact with the right end portion of the peripheral surface of the photoconductive drum 7, falls within the range of the second cleaning member 114 b disposed in contact with the right end portion of the peripheral surface of the photoconductive drum 7. Further, the inward edge 114 b 1 of the first cleaning member 114 b is outside the range Ld, in terms of the lengthwise direction of the photoconductive drum 7, across which the development process is carried out by the development roller 10 d, and inside the range Lc, across which the charge roller 8 is in contact with the photoconductive drum 7.

[0184] With the provision of the above described structural arrangement, the toner particles adhering to the photoconductive drum 7 can be removed by taking them into the first and second cleaning members 114 a and 114 b.

[0185] Therefore, the stray toner particles do not agglomerate on the peripheral surface of the photoconductive drum 7, across the areas corresponding to the ranges across which the cap-like rollers 10 m (10 m 1 and 10 m 2) remain in contact with the photoconductive drum 7. Therefore, the distance between the photoconductive drum 7 and development roller 10 d is kept constant, making it possible to form an excellent image.

[0186] In particular, not only does the usage of a laminar material, for example, a laminar combination of a layer or elastic substance and a layer of nonwoven fabric, as the materials for the cleaning members 114 make it possible to prevent the stray toner particles from adhering to the photoconductive drum 7. Across the areas corresponding to the ranges across which the cap-like rollers 10 m (10 m 1 and 10 m 2) remain in contact with the photoconductive drum 7, without increasing component count, but also to produce a sturdy and resilient cleaning member, and to improve assembly quality and efficiency. In other words, not only does it make it possible to form an excellent image, but also to minimize the cost of the process cartridge B.

[0187] Further, the above described structural arrangement makes it possible for the first and second cleaning members 114 a and 114 b to remove the toner particles adhering the peripheral surface of the photoconductive drum 7, across the range in which the photoconductive drum 7 is not charged, that is, outside the range across which the charge roller 8 is in contact with the photoconductive drum 7. Therefore, toner particles are prevented from adhering to the image edges and/or recording medium edges. Therefore, it is possible to form an excellent image.

[0188] In this embodiment, the pair of cleaning members 114 (114 a and 114 b) are disposed in contact with the lengthwise ends of the photoconductive drum 7, one for one. However, it may be only one of lengthwise ends of the photoconductive drum 7 that is provided with the cleaning member 114.

[0189] (Mounting and Removal of Process Cartridge B, into and from, Image Forming Apparatus Main Assembly)

[0190] In order to form an image, the process cartridge B assembled as described above is mounted into the image forming apparatus main assembly A0. Next, referring to FIGS. 22-27, it is described how the process cartridge B is mounted.

[0191] As described before with reference to FIG. 20, as the hard tab 10 g 2 is separated from the end member of the development unit D of the process cartridge B, and is pulled in the direction indicated by the arrow mark, the toner sealing member 27 is pulled out of the process cartridge B, allowing the toner to be supplied into the development chamber 10 j; the process cartridge is readied.

[0192] As will be understood with reference to FIG. 4 in addition to FIG. 20, the side holder 107 attached to the cartridge frame (drum supporting frame 102) of the process cartridge B is provided with an arcuate portion (first engagement portion) 107 d, as a guide, by which the process cartridge B is guided when it is mounted into the image forming apparatus main assembly A0; arcuate portion (second engagement portion) 107 c, as a rotational control portion, which controls the attitude of the process cartridge B when the process cartridge B is mounted into the image forming apparatus main assembly A0. The arcuate portion 107 d is at the bottom of the cartridge frame, and the center of its curvature coincides with the axial line of the photoconductive drum 7, whereas the arcuate portion 107 e is located at the corner of the side holder 107.

[0193] In terms of the drum shaft direction of the development unit D, the arcuate portion 107 d is on the outward side of the drum unit D, but, as seen from the drum shaft direction, it partially overlaps with the drum unit D. Also in terms of the drum shaft direction, the rotation control portion 107 e is on the outward side of the drum unit D, and, as seen from the axial direction of the photoconductive drum 7 of the development unit D, it falls within the projection of the development unit D. Further, in terms of the direction in which the process cartridge B is inserted into the image forming apparatus main assembly A0, the rotation control portion 107 e is on the trailing side of the arcuate portion 107 d.

[0194] In this embodiment, the triangular coupling portion 7 a 1, which catches the driving force from the image forming apparatus main assembly A0 is on the inward side of the side holder 107, in terms of the drum shaft direction. With this positional arrangement, the process cartridge B does not need to be provided with dedicated positioning portions such as the cover portion 50 of the triangular coupling portion 7 a 1 and projection 51 of the process cartridge in accordance with the prior arts, shown in FIG. 30, which function as a positioning portion (positioning boss CB) and a guide, respectively. Therefore, it is possible to make the cartridge size smaller compared to a cartridge in accordance with the prior arts.

[0195] Referring to FIGS. 22 and 24, the image forming apparatus main assembly A0 is provided with a guiding portion Ga as a first guide which guides the process cartridge B into the image formation position (properly mounted position), by the aforementioned arcuate portion 107 d and rotation control portion 107 e of the process cartridge B; the arcuate portion 107 d and rotation control portion 107 e are rested on the guiding portion Ga and are allowed to slide thereon.

[0196] On the other hand, the process cartridge B is provided with a projection 102 a for covering the drum supporting shaft 100, and a projection 102 b for controlling the process cartridge position during the mount or removal of the process cartridge B. The projection 102 a and 102 b protrude from the end surface of the drum supporting frame 102 on the side opposite to the end surface with the side holder 107, in terms of the drum shaft direction, as will be easily understood with reference to FIG. 3 in addition to FIGS. 22 and 24.

[0197] Further, referring to FIGS. 23 and 25, the image forming apparatus main assembly A0 is provided with a guiding portion Cb as a second cartridge guide on the main assembly side, which coordinates with the side holder 107 in order to maintain the altitude of the process cartridge B set by the side holder 107 so that the process cartridge B does not become tilted relative to the drum shaft direction.

[0198] Next, referring to FIGS. 22-25, the steps to be followed in order to mount the process cartridge B into the image forming apparatus main assembly A0 will be described.

[0199] First, the a lid 6 a which also serves as a delivery tray 6 of the image forming apparatus main assembly A0 is opened to expose the guiding portions Ga and Gb of the apparatus main assembly A0. Then, the process cartridge B is to be held so that its arcuate portion 107 d and rotation control portion 107 e are on the front and rear sides, respectively, as indicated by the single-dot line in FIGS. 22 and 23. Then, the arcuate portion 107 d and rotation control portion 107 e are to be rested on the first guiding surface Ga1, the front portion of which is somewhat undulatory, while holding the process cartridge B in the above described manner. On the other side, therefore, the projections 102 a and 102 b of the process cartridge B are rested on the first guiding surface Gb1 of the guiding portion Gb.

[0200] Then, the process cartridge B set in the above described manner is to be pushed into the image forming apparatus main assembly A0.

[0201] As the process cartridge B is pushed, the arcuate portion 107 d and rotation control portion 107 e of the process cartridge B are guided to their designated image formation positions, while sliding on, being thereby guided by, the second guiding surface Ga2 of the guiding portion Ga, which is roughly perpendicular to the first guiding surface Ga1, the third guiding surface Ga3 of the guiding portion Ga, which roughly horizontally extends from the bottom of the second guiding surface Ga2, and the fourth guiding surface Ga4 of the guiding portion Ga, which extends from the inward end of the third guiding surface Ga3 in an arcuately dipping manner.

[0202] As a result, the process cartridge B rests on the third guiding surface Ga3, with its arcuate portion 107 d being in contact with the fourth guiding surface Ga4, as a first portion of catching and supporting the process cartridge B, and the curved surface of the rear portion of the rotation control portion 107 e being In contact with the second guiding surface Ga2, as shown in FIG. 26. In this state, the transfer roller 4 and photoconductive drum 7 have come into contact with each other, and therefore, the process cartridge B has come under the pressure working in the direction indicated by an arrow mark in FIG. 26. As a result, the third contact portion 107 g is placed in contact with the second guiding surface Ga2 adjacent to the third guiding surface Ga3, preventing the positional deviation of the process cartridge B. The third contact portion 107 g may be either integral with the second contact portion (rotation control portion) 107 e, or discrete.

[0203] On the other hand, the projections 102 a and 102 b, which are on the other side of the process cartridge B, are guided to their designated image formation positions while sliding on, being thereby guided by, the second guiding surface Gb2 of the guiding portion Gb, which is roughly perpendicular to the first guiding surface Gb1, the third guiding surface Gb3 of the guiding portion Gb, which roughly horizontally extends from the bottom of the second guiding surface Gb2, and the fourth guiding surface Gb4 of the guiding portion Gb, which extends from the inward end of the third guiding surface Gb3 in an arcuately dipping manner.

[0204] As a result, the process cartridge B rests on the third guiding surface Gb3, with its projections 102 a and 102 b being between the fourth guiding surface Gb4, as a second portion for catching and supporting the process cartridge B, and the second guiding surface Gb2, as shown in FIG. 28.

[0205] As a result, the process cartridge B is mounted into the proper position in the apparatus main assembly. Next, the lid 6 a of the image forming apparatus main assembly A0 is to be closed. As the lid 6 a is closed, the triangular coupling portion 7 a 1 of the cartridge B couples with the driving force transmitting member 200, shown in FIG. 24, having the roughly triangular twisted hole, allowing the rotational driving force to be transmitted from the image forming apparatus main assembly A0 to the process cartridge B.

[0206] As a result, the process cartridge B is rotated about the rotational axis of the triangular coupling portion 7 a 1 having coupled as shown in FIG. 27, which coincides with the rotational axis of the photoconductive drum 7. Consequently, gaps x and y are created between the arcuate portion 107 d and contact portion 107 g of the process cartridge B, and the fourth guiding surface Ga4 add second guiding surface Ga2 of the guiding portion Ga, respectively, and the rotation control portion 107 e of the side holder 107 comes into contact with the third guiding surface Ga3, as a regulating surface, of the guiding portion Ga, fixing thereby the attitude of the process cartridge B in terms of the rotation of the process cartridge B about the rotational axis of the photoconductive drum 7.

[0207] On the other side of the process cartridge B in terms of the drum shaft direction, as the process cartridge B is mounted into the image forming apparatus main assembly A0, the projection 102 a of the drum supporting frame 102, the axial line of which coincides with that of the photoconductive drum 7, settles into the U-shaped groove, as a cartridge positioning portion, that is, the fourth guiding surface Gb4, and is kept there by the force generated by the resiliency of the transfer roller 4 and the force from a spring (unshown) for preventing the formation of a blurred image traceable to the driving of the process cartridge B. As for the other projection, that is, the projection 102 b, of the drum supporting frame 102, it is designed in position and size so that after the proper mounting of the process cartridge B into the image forming apparatus main assembly A0, it remains in noncontact with the image forming apparatus main assembly A0, as long as the component dimension errors and assembly errors of the image forming apparatus main assembly A0 are within the normal tolerance.

[0208] The above described attitude of the process cartridge B is the attitude in which the process cartridge B is kept during an image forming operation. Thus, an image forming operation can be started as soon as the process cartridge B assumes this attitude in the image forming apparatus main assembly A0.

[0209] In order to extract the process cartridge B from the image forming apparatus main assembly A0, the above described cartridge mounting steps are to be carried out in reverse. As the process cartridge B is pulled, the process cartridge B comes out of the apparatus main assembly, with the arcuate portion) 107 d and rotation control portion 107 e sliding on the guiding portion Ga, and the projections 102 a and 102 b sliding on the guiding portion Gb. During this process of extracting the process cartridge B from the image forming apparatus main assembly A0, the arcuate portion 107 d, and the top surface 107 f opposing the rotation control portion 107 e across the cartridge mounting space, function as the cartridge position controlling means on the side holder side 107 side, and the projections 102 a and 102 b function as the cartridge position controlling means on the side opposite to the side holder 107 side.

[0210] In particular, when the process cartridge B is removed from the image formation position, the projection 102 b comes into contact with the fifth guiding surface Gb5, which is the top surface of the guiding portion Gb, preventing thereby the front side of the process cartridge B, in terms of the cartridge extraction direction, from rotating upward more than a predetermined angle.

[0211] It is not mandatory that the contours of the above described first, second, and third contact portions of the process cartridge B 200 are as described above. For example, the first and second contact portions may be polygonal (200 and 201, respectively) as shown in FIG. 29. Further, the second contact portion may have ridges 202 as shown in FIG. 30, as long as the counters of these contact portions perform the above described cartridge positioning functions. It is preferable, however, that the first, second, and third contact portion of the process cartridge B are arcuate, because when they are arcuate, a part of the second contact portion is allowed to come into contact with the fourth guiding surface Ga4, even if the process cartridge B deviates in attitude due to the tolerance in component dimension.

[0212] The above described embodiment of the present invention is compatible with various well-known developing methods, for example, the two-component magnetic brush developing method, cascade developing method, touch-down developing method, cloud developing, etc.

[0213] As for the electrophotographic photoconductive substance compatible with the above described embodiment, such a photoconductive substance as amorphous silicon, amorphous selenium, zinc oxide, titanium oxide, and various organic photoconductors, can be included. Incidentally, the photoconductive drum in this embodiment comprises a cylinder formed of aluminum alloy or the like, and a layer of photoconductive substance placed on the entirety of the peripheral surface of the cylinder by deposition, painting, or the like.

[0214] As for the material for the drum supporting frame, toner storage-developing means frame, frame lid, etc., of a process cartridge in accordance with the present invention, there are such plastics as polystyrene, ABS (acrylonitrile-butadiene-styrene copolymer), denatured PPE resin (polyphenylene-ether), denatured PPO resin (polyphenylene oxide), polycarbonate, polyethylene, polypropylene, etc.

[0215] The above described process cartridge is, for example, a cartridge comprising an electrophotographic photoconductive member, a developing means, and at least one more processing means. In other words, the present invention is compatible with: a cartridge in which an electrophotographic photoconductive member, a developing means, and a charging means are integrally disposed, and which is removably mountable in the main assembly of an image forming apparatus; a cartridge in which an electrophotographic photoconductive member and a developing means are integrally disposed, and which is removably mountable in the main assembly of an image forming apparatus; and the like, in addition to the process cartridge B in the above described embodiment of the present invention.

[0216] In other words, the present invention is also compatible with: a cartridge in which an electrophotographic photoconductive member, and a charging means or a developing means, are integrally disposed, and which is removably mountable in an image forming apparatus; a process cartridge in which a charging means, a developing means, and an electrophotographic photoconductive member are integrally disposed, and which is removably mountable in an image forming apparatus; and a cartridge in which a minimum of a developing means and an electrophotographic photoconductive member are integrally disposed, and which is removably mountable in an image forming apparatus.

[0217] The image forming apparatus in the above described embodiment of the present invention is a laser beam printer. However, the application of the present invention is not limited to a laser beam printer. In other words, the present invention is also applicable to various image forming apparatuses other than a laser beam printer, for example, an electrophotographic copying machine, a facsimileing apparatus, a wordprocessor, etc., which is obvious.

[0218] As described in the foregoin, according to the foregong embodiments of the present invention, the charging roller as well as the photosensitive drum, the developing roller and the transfer roller in the process cartridge, can be rotationally driven in a stabilized manner.

[0219] In addition, the strength of the drum gear can be improved.

[0220] While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. 

What is claimed is:
 1. An electrophotographic photosensitive drum for a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, wherein said process cartridge includes a charging roller for electrically charging said photosensitive drum and a developing roller for developing an electrostatic latent image formed on said photosensitive drum, said photosensitive drum comprising: (i) a cylinder hating a photosensitive layer on the peripheral surface thereof; (ii) a drum helical gear, mounted to one end of said cylinder, for transmiting a rotational driving force to a transfer roller provided in a main assembly of said apparatus and for transmiting a rotational driving force to said charging roller and said developing roller, wherein the transfer roller is effective to transfer the developed image formed on said electrophotographic photosensitive drum onto a recording material; (iii) a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; (iv) a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; wherein said electrophotographic photosensitive drum, when it is mounted to a cartridge frame of said process cartridge, permits insertion of the cartridge frame to enter said gap so that shaft portion is rotatably supported in said cartridge frame.
 2. An electrophotographic photosensitive drum according to claim 1, wherein said drum helical gear includes a first helical gear portion positioned at an outside with respect to the longitudinal direction of said cylinder and a second helical gear portion positioned at an inside; said first helical gear portion and said second helical gear portion are juxtaposed with each other; twisting directions of helical teeth of said helical gear portions are different from each other; said first helical gear portion is effective to transmit a rotational driving force to said charging roller and said transfer roller; and said second helical gear portion is effective to transmit a rotational driving force to said developing roller.
 3. An electrophotographic photosensitive drum according to claim 1 or 2, wherein the helical teeth of said first helical gear portion is twisted rightwardly, and the helical teeth of said second helical gear portion is twisted leftwardly as seen from a position where said drum helical gear portion is dispoed with respect to a longitudinal direction of said drum cylinder; when said process cartridge is mounted to the main assembly of the apparatus, and said electrophotographic photosensitive drum is rotated, said first helical gear portion produces an urging force away from said drum helical gear portion, and said second helical gear portion produced an urging force to said drum helical gear portion.
 4. An electrophotographic photosensitive drum for a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, wherein said process cartridge includes a charging roller for electrically charging said photosensitive drum and a developing roller for developing an electrostatic latent image formed on said photosensitive drum, said photosensitive drum comprising: (i) a cylinder having a photosensitive layer on the peripheral surface thereof; (ii) a drum helical gear mounted to one end of said cylinder and including a first helical gear portion positioned at all outside with respect to the longitudinal direction of said cylinder and a second helical gear portion positioned at an inside; said first helical gear portion and said second helical gear portion are juxtaposed with each other; twisting directions of helical teeth of said helical gear portions are different from each other; said first helical gear portion is effective to transmit a rotational driving force to said charging roller and said transfer roller; and said second helical gear portion is effective to transmit a rotational driving force to said developing roller; wherein the helical teeth of said first helical gear portion is twisted rightwardly, and the helical teeth of said second helical gear portion is twisted leftwardly as seen from a position where said drum helical gear portion is dispoed with respect to a longitudinal direction of said drum cylinder; when said process cartridge is mounted to the main assembly of the apparatus, and said electrophotographic photosensitive drum is rotated, said first helical gear portion produces an urging force away from said drum helical gear portion, and said second helical gear portion produced an urging force to said drum helical gear portion. (iii) a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; (iv) a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; wherein said electrophotographic photosensitive drum, when it is mounted to a cartridge frame of said process cartridge, permits insertion of the cartridge frame to enter said gap so that shaft portion is rotatably supported in said cartridge frame.
 5. An electrophotographic photosensitive drum according to claim 5, wherein an end surface of said shaft portion is positioned inside an end surface of said drum helical gear with respect to a longitudinal direction, and said projection is at least partly overlapped with said end surface of said drum helical gear.
 6. An electrophotographic photosensitive drum according to claim 5, wherein said projection has a polygonal cross-section taken aling a plane crossing with a direction or a rotational axis, and is twisted, and said hole has a polygonal cross-section taken along a plane crossing with the direction of the rotational axis, and is twisted.
 7. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, comprising: (i) a cartridge frame; (ii) a charging roller; (iii) a developing roller; (iv) an electrophotographic photosensitive drum which includes, a cylinder having a photosensitive layer on the peripheral surface thereof; a drum helical gear, mounted to one end of said cylinder, for transmiting a rotational driving force to a transfer roller provided in a main assembly of said apparatus and for transmiting a rotational driving force to said charging roller and said developing roller, a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus, wherein said cartridge frame enters said gap to rotatably support said shaft portion.
 8. A process cartridge according to claim 1, wherein said drum helical gear includes a first helical gear portion positioned at an outside with respect to the longitudinal direction of said cylinder and a second helical gear portion positioned at an inside; said first helical gear portion and said second helical gear portion are juxtaposed with each other; twisting directions of helical teeth of said helical gear portions are different from each other; wherein said first helical gear portion has a diameter between tooth tops which is smaller than a diameter between tooth tops of said second helical gear portion; said first helical gear portion is effective to transmit a rotational driving force to said charging roller and said transfer roller; and said second helical gear portion is effective to transmit a rotational driving force to said developing roller.
 9. A process cartridge according to claim 7 or 8, wherein the helical teeth of said first helical gear portion is twisted rightwardly, and the helical teeth of said second helical gear portion is twisted leftwardly as seen from a position where said drum helical gear portion is dispoed with respect to a longitudinal direction of said drum cylinder; when said process cartridge is mounted to the main assembly of the apparatus, and said electrophotographic photosensitive drum is rotated, said first helical gear portion produces an urging force away from said drum helical gear portion, and said second helical gear portion produced an urging force to said drum helical gear portion.
 10. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising: (i) cartridge frame; (ii) a charging roller; (iii) a developing roller; (iv) an electrophotographic photosensitive drum which includes, a cylinder having a photosensitive layer on a peripheral surface thereof; a drum helical gear mounted to one end of said cylinder and including a first helical gear portion positioned at an outside with respect to the longitudinal direction of said cylinder and a second helical gear portion positioned at an inside; said first helical gear portion and said second helical gear portions are juxtaposed with each other; twisting directions of helical teeth of said helical gear portions are different from each other; said first helical gear portion is effective to transmit a rotational driving force to said charging roller and said transfer roller; and said second helical gear portion is effective to transmit a rotational driving force to said developing roller; wherein the helical teeth of said first helical gear portion is twisted rightwardly, and the helical teeth of said second helical gear portion is twisted leftwardly as seen from a position where said drum helical gear portion is dispoed with respect to a longitudinal direction of said drum cylinder; when said process cartridge is mounted to the main assembly of the apparatus, and said electrophotographic photosensitive drum is rotated, said first helical gear portion produces an urging force away from said drum helical gear portion, and said second helical gear portion produced an urging force to said drum helical gear portion; (v) a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; (vi) a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; wherein said electrophotographic photosensitive drum, when it is mounted to a cartridge frame of said process cartridge, permits insertion of the cartridge frame to enter said gap so that shaft portion is rotatably supported in said cartridge frame.
 11. A process cartridge according to claim 8 or 10, wherein an end surface of said shaft portion is positioned inside an end surface of said drum helical gear with respect to a longitudinal direction, and said projection is at least partly overlapped with said end surface of said drum helical gear.
 12. A process cartridge according to claim 11, wherein said projection has a polygonal cross-section taken aling a plane crossing with a direction of a rotational axis, and is twisted, and said hole has a polygonal cross-section taken along a plane crossing with the direction of the rotational axis, and is twisted.
 13. An electrophotographic image forming apparatus for forming an image on a recording material, to which a process cartridge is detachably mountable, said apparatus comprising: (i) a transfer roller; (ii) a process cartridge mounting portion for detachably mounting a process cartridge, said process cartridge including, a cartridge frame; a charging roller; a developing roller: a photosensitive drum which includes, a cylinder having a photosensitive layer on the peripheral surface thereof; a drum helical gear, mounted to one end of said cylinder, for transmiting a rotational driving force to a transfer roller provided in a main assembly of said apparatus and for transmiting a rotational driving force to said charging roller and said developing roller, a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; wherein said cartridge frame enters said gap to rotatably support said shaft portion.
 14. An electrophotographic image forming apparatus for forming an image on a recording material, to which a process cartridge is detachably mountable, said apparatus comprising: (i) a transfer roller; (ii) a process cartridge mounting portion for detachably mounting a process cartridge, said process cartridge including, a cartridge frame; a charging roller; a developing roller; a cylinder having a photosensitive layer on the peripheral surface thereof; a drum helical gear mounted to one end of said cylinder and including a first helical gear portion positioned at an outside with respect to the longitudinal direction of said cylinder and a second helical gear portion positioned at an inside; said first helical gear portion and said second helical gear portion are juxtaposed with each other; twisting directions of helical teeth of said helical gear portions are different from each other; said first helical gear portion is effective to transmit a rotational driving force to said charging roller and said transfer roller; and said second helical gear portion is effective to transmit a rotational driving force to said developing roller; wherein the helical teeth of said first helical gear portion is twisted rightwardly, and the helical teeth of said second helical gear portion is twisted leftwardly as seen from a position where said drum helical gear portion is dispoed with respect to a longitudinal direction of said drum cylinder; when said process cartridge is mounted to the main assembly of the apparatus, and said electrophotographic photosensitive drum is rotated, said first helical gear portion produces an urging force away from said drum helical gear portion, and said second helical gear portion produced an urging force to said drum helical gear portion; a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; wherein said electrophotographic photosensitive drum, when it is mounted to a cartridge frame of said process cartridge, permits insertion of the cartridge frame to enter said gap so that shaft portion is rotatably supported in said cartridge frame.
 15. An electrophotographic photosensitive drum for a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said photosensitive drum, wherein said process cartridge includes a charging roller for electrically charging said photosensitive drum and a developing roller for developing an electrostatic latent image formed on said photosensitive drum, said photosensitive drum comprising: (i) a cylinder having a photosensitive layer on the peripheral surface thereof: (ii) a drum helical gear, mounted to one end of said cylinder, for transmitting a rotational driving force to a transfer roller provided in a main assembly of said apparatus and for transmiting a rotational driving force to said charging roller and said developing roller, wherein the transfer roller is effective to transfer the developed image formed on said electrophotographic photosensitive drum onto a recording material; (iii) a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; (iv) a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; wherein said electrophotographic photosensitive drum, when it is mounted to a cartridge frame of said process cartridge, permits insertion of the cartridge frame to enter said gap so that shaft portion is rotatably supported in said cartridge frame, wherein said drum helical gear includes a first helical gear portion positioned at an outside with respect to the longitudinal direction of said cylinder and a second helical gear portion positioned at an inside; said first helical gear portion and said second helical gear portion are juxtaposed with each other; twisting directions of helical teeth of said helical gear portions are different from each other; said first helical gear portion is effective to transmit a rotational driving force to said charging roller and said transfer roller; and said second helical gear portion is effective to transmit a rotational driving force to said developing roller, wherein the helical teeth of said first helical gear portion is twisted rightwardly, and the helical teeth of said second helical gear portion is twisted leftwardly as seen from a position where said drum helical gear portion is dispoed with respect to a longitudinal direction of said drum cylinder; when said process cartridge is mounted to the main assembly of the apparatus, and said electrophotographic photosensitive drum is rotated, said first helical gear portion produces an urging force away from said drum helical gear portion, and said second helical gear portion produced an urging force to said drum helical gear portion, wherein said projection has a polygonal cross-section taken aling a plane crossing with a direction of a rotational axis, and is twisted, and said hole has a polygonal cross-section taken along a plane crossing with the direction of the rotational axis, and is twisted.
 16. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, comprising: (i) a cartridge frame; (ii) a charging roller: (iii) a developing roller; (iv) an electrophotographic photosensitive drum which includes, a cylinder having a photosensitive layer on the peripheral surface thereof; a drum helical gear, mounted to one end of said cylinder, for transmiting a rotational driving force to a transfer roller provided in a main assembly of said apparatus and for transmiting a rotational driving force to said charging roller and said developing roller, a shaft portion provided at a central portion of said drum helical gear at a position where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus, wherein said cartridge frame enters said gap to rotatably support said shaft portion, wherein said drum helical gear includes a first helical gear portion positioned at an outside with respect to the longitudinal direction of said cylinder and a second helical gear portion positioned at an inside; said first helical gear portion and said second helical gear portion are juxtaposed with each other; twisting directions of helical teeth of said helical gear portions are different from each other; wherein said first helical gear portion has a diameter between tooth tops which is smaller than a diameter between tooth tops of said second helical gear portion; said first helical gear portion is effective to transmit a rotational driving force to said charging roller and said transfer roller; and said second helical gear portion is effective to transmit a rotational driving force to said developing roller, wherein the helical teeth of said first helical gear portion is twisted rightwardly, and the helical teeth of said second helical gear portion is twisted leftwardly as seen from a position where said drum helical gear portion is dispoed with respect to a longitudinal direction of said drum cylinder; when said process cartridge is mounted to the main assembly of the apparatus, and said electrophotographic photosensitive drum is rotated, said first helical gear portion produces an urging force away from said drum helical gear portion, and said second helical gear portion produced an urging force to said drum helical gear portion, wherein said projection has a polygonal cross-section taken aling a plane crossing with a direction of a rotational axis, and is twisted, and said hole has a polygonal cross-section taken along a plane crossing with the direction of the rotational axis, and is twisted.
 17. An electrophotographic image forming apparatus for forming an image on a recording material, to which a process cartridge is detachably mountable, said apparatus comprising: (i) a transfer roller; (ii) a process cartridge mounting portion for detachably mounting a process cartridge, said process cartridge including, a cartridge frame; a charging roller; a developing roller; an electrophotographic photosensitive drum which includes, a cylinder having a photosensitive layer on the peripheral surface thereof; a drum helical gear, mounted to one end of said cylinder, for transmiting a rotational driving force to a transfer roller provided in a main assembly of said apparatus and for transmiting a rotational driving force to said charging roller and said developing roller, a shaft portion provided at a central portion of said drum helical gear at a positive where it is completely overlapped with a teeth of said drum helical gear with respect to a longitudinal direction of said cylinder, wherein a gap is provided between said teeth and a peripheral surface of said shaft portion; a projection, provided at a free end of said shaft portion, for engagement with a hole formed in the main assembly of the apparatus to receive a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus, wherein said cartridge frame enters said gap to rotatably support said shaft portion, wherein said drum helical gear includes a first helical gear portion positioned at an outside with respect to the longitudinal direction of said cylinder and a second helical gear portion positioned at an inside; said first helical gear portion and said second helical gear portion are juxtaposed with each other; twisting directions of helical teeth of said helical gear portions are different from each other; wherein said first helical gear portion has a diameter between tooth tops which is smaller than a diameter between tooth tops of said second helical gear portion; said first helical gear portion is effective to transmit a rotational driving force to said charging roller and said transfer roller; and said second helical gear portion is effective to transmit a rotational driving force to said developing roller, wherein the helical teeth of said first helical gear portion is twisted rightwardly, and the helical teeth of said second helical gear portion is twisted leftwardly as seen from a position where said drum helical gear portion is dispoed with respect to a longitudinal direction of said drum cylinder; when said process cartridge is mounted to the main assembly of the apparatus, and said electrophotographic photosensitive drum is rotated, said first helical gear portion produces an urging force away from said drum helical gear portion, and said second helical gear portion produced an urging force to said drum helical gear portion, wherein said projection has a polygonal cross-section taken aling a plane crossing with a direction of a rotational axis, and is twisted, and said hole has a polygonal cross-section taken along a plane crossing with the direction of the rotational axis, and is twisted. 